Security - Ideas Please

I have an '04 xl700 and would like to add some sort of keyed kill switch or security shut off.

We taking it on day trips, loving it and visiting great areas, but I'm always worried when tied up at the docks that anyone can jump on the thing and go. My other option is to cable lock it to the dock, but there are other times when we anchor near small beaches and I have the same concerns.

Any advise, ideas, or sources for adding a keyed switch I can splice in-line with the cutoff switch would be great. Any other ideas for security appreciated as well!